The present invention relates to hinges, and more particularly to a structurally improved door hinge which ensures more easy and smooth operation and will not be askew or deformed, therefore durability.
Prior art door hinge as shown in FIG. 1 which generally comprises a double tubed base 10, a pair of torsion springs 12 placed in the tubes 11, which end of the tubes 11 is rotatably engaged a twisting member 13 or 13' each has a slot 131 on lower portion for anchoring the ends 121 of the spring 12 and a plurality of transverse recesses 132 spacedly formed around the outer periphery of the upper portion of the twisting member 13 for adjusting the tensions of the spring 12 by a dowel pin 14, a pair of lug members 20 coupled with the base 10 on their ears 21 in alignment with the ends of the tubes 11 and a threaded rod 22 inserted through the center of the tube 11 and exposed to outside the ears 21 and then fastened by a pair of cap nuts 23. Therefore a door hinge of the prior art is constructed as shown in FIG. 2. This door hinge provides automatic door closing for the exertion of the tension force energised in the pair of torsion springs 12. However, the twisting member 13 thereof is currently made of metal material which is expensive and difficult to manufacture. Furthermore, the rigid surface of its stepped upper portion which is pressedly engaged within the tube 11 will enlarge the caliber of the tube 11 during frequent swinging the twisting member 13 therein and deforms the hinge so as to tend to skew the door after all. Besides, the twisting member 13 is axially engaged with the threaded rod 23 which is also made of metal material, the swinging between them will cause frictional noise. If there is any split in the slot 131, it will be breakable for the torsion force of the spring 12.